Thanks y'all! The hoodie was one of my lucky finds from HomeSense, the only store where I ever have a hope of finding xxsmall doggie clothes. It only cost me £7.99. It's a Canadian brand I've never come across before called Great Jack's - does anybody know of it? I can't find it online.
I had a rather scary moment last week where Florrie got over-chilled and wouldn't stop shivering, which really brought home to me how essential it is to keep her little body warm. (It took several layers of clothing, a fluffy blanket and lots of cuddles to get her back to normal.) The new sweater is really thick, and fits her perfectly...although I have to say that she's less than thrilled by the hood. It was pulled up only for the photo, which is a shame, as she looks so gorgeous!